Paperboard cartons with laminated reinforcing ribbons and method of making same

ABSTRACT

A method of making reinforced paperboard cartons comprises the steps of advancing a web of paperboard along a path and progressively laminating at least one ribbon of reinforcing material to the advancing web of paperboard. The ribbon of reinforcing material, which also may be paperboard, has a width less than the width of the web of paperboard and is applied with adhesive at a selected location across the width of the web. The web and its laminated ribbon are cut into sheets of a predetermined size and the sheets are die-cut and scored with fold lines to form carton blanks. The carton blanks are subsequently formed into cartons for receiving articles, the laminated reinforcing material providing reinforcement in selected portions of the cartons. Multiple ribbons and multiple layers of ribbons may be laminated to the web in respective selected locations to provide reinforcement in more than one portion of the cartons. Reinforced cartons and carton blanks made by the method also are provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to article packaging and morespecifically to the fabrication of paperboard cartons into which aplurality of articles can be packaged for transport and sale.

2. Description of the Related Art

Paperboard cartons of various design and construction have long beenused by the packaging industry to package a wide variety of articlessuch as canned and bottled drinks, food items, detergents, and more. Ingeneral, paperboard cartons are erected or converted from paperboardblanks that are die-cut or rotary-cut from long webs of paperboard asthe paperboard is drawn progressively from large rolls. Fold lines arescored in the blanks to define the various panels of the cartons and toaid in the conversion of the blanks into their final carton shapes. Insome cases, such as in beer and soft drink packaging, the blanks arepre-glued and provided to packager in the form of substantially flatknocked down sleeves that are erected in a packaging machine into openended cartons for receiving articles. In other cases, the blanks areprovided in a completely flat configuration, in which case the blankstypically are folded around groups of articles and glued by thepackaging machine. In either case, the conversion of blanks usually isperformed at the time of packaging by specialized conversion stationsthat are part of large continuous packaging machines. In this way, theflat or pre-glued and knocked down paperboard blanks can be shippedeconomically to the packager in palletized stacks.

When making paperboard carton blanks from a web of paperboard, the webusually is pre-cut to a specified predetermined width from a wider webof paperboard stock. The pre-cutting of the web to width generally takesplace at the paper mill. The width of the web in each case is dictatedby the size and shape of the cartons to be made from the web and isspecified to the paper mill by a carton fabricator. For example, a webof paperboard stock may have a width of 64 inches whereas a particularcarton blank may require a web 48 inches wide. In such an example, astrip of paperboard 16 inches wide (or two strips that total 16 inchesin width) typically will be cut from the web of paperboard stock by thepaper mill to form the required 48 inch-wide web. These strips, known inthe industry as “trim,” traditionally have had reduced value and in somecases are sold at low cost for secondary uses such as the making ofshirt collar stiffeners used in the garment industry. In general, thecreation of trim in the process of making paperboard web has long been aproblem for paperboard manufacturers.

Occasionally, errors by paperboard manufacturers result in rolls ofpaperboard web that may be substandard for a variety of reasons and thusnot usable in the fabrication of paperboard cartons. In other cases,paperboard web manufactured for a particular customer may not meetspecifications and thus cannot readily be used. Such substandardand-off-spec paperboard is known in the industry as “cull” and also hashad reduced value, sometimes being reconstituted into pulp for makingnew paper. In general, there has been little use for trim and cull inthe paperboard carton making industry.

In many packaging applications, the cartons into which articles arepackaged must exhibit enhanced strength at least in selected regions tocontain the articles securely. This is particularly true in cases wherethe articles are relatively heavy and are stacked atop one another intheir cartons for shipment and sale. For example, canned and bottledbeverages, which typically may be packaged in groups of 6, 12, or 24,are inherently relatively heavy and typically are stacked severalcartons high on pallets for shipment to retail stores. The cartons intowhich these beverages are packed therefore must be strong enough to holdthe groups of cans or bottles securely together and to resist tearing or“blowing out” even when under the substantial weight of several layersof stacked cartons. In other applications, such as, for example, cartonsof boxed fruit drinks, the cartons themselves must provide at least someof the strength and rigidity necessary to resist crushing when layers ofcartons are stacked atop one another. This is because the individualdrink containers lack the rigidity of bottles or cans and cannotthemselves bear the entire weight of a stack of cartoned fruit drinks.

In applications such as these, traditional paperboard cartons havesometimes proven inadequate to provide the required strength andrigidity. As a result, many packagers have turned to a carton materialknown in the industry as micro-flute, which is a corrugated paperproduct. In general, micro-flute is fabricated from a core of papermaterial formed with a large number of relatively small corrugationssandwiched between facing sheets of flat paper. Micro-flute does tend toprovide the strength and rigidity required in many packagingapplications; however, it also has significant inherent problems andshortcomings including its generally higher price compared topaperboard. In addition, carton blanks made of micro-flute can be moreexpensive in some weights to ship than paperboard blanks because theirgreater thickness limits the number of blanks that can be stacked onstandard sized pallet. Further, in some cases, specialized conversionmachinery is required to convert the blanks to cartons, increasing thecost of the packaging process. Finally, the printing of high qualitygraphics on micro-flute has sometimes proven to be difficult. Thus,micro-flute has not provided a completely satisfactory solution as acarton making material in packaging applications where enhanced cartonstrength and rigidity is required.

Attempts have been made to improve the strength and rigidity ofpaperboard cartons to provide a viable alternative to micro-flute whereadded strength and rigidity are required. These attempts have includedlaminating two or more webs or sheets of standard thickness paperboardtogether to create thicker multi-ply paperboard from which carton blankscan be cut. However, while this approach increases the strength andrigidity of resulting cartons, it essentially results in a doubling ofthe paperboard required per carton and a consequent increase in materialand shipping costs. Further, the formation of fold lines in and thefolding of multiple ply paperboard cartons is problematic due to theadded thickness of paperboard that must be folded. For these and otherreasons, such multi-layer laminated paperboard has not proven to be anacceptable alternative to micro-flute.

Other attempts to provide alternatives to micro-flute have included theseparate fabrication of custom stiffening inserts, which are installedin individual cartons after the cartons are converted from cartonblanks. Such inserts have been used, for example, in detergent cartonsto provide added strength for stacking and an internal moisture barrierand in beverage cartons to provide separators. However, installinginserts requires expensive specialized machinery, increases material andpackaging costs, and can significantly slow the packaging process.

A problem with cartons in general, including micro-flute and paperboardcartons, is that they tend to tear and fail in areas of particularlyhigh stress such as in certain corners of the cartons where foldedpanels meet. Such tears, once started, often can do spread, resulting inthe separation of carton panels and ultimately in carton blow-out.Attempts to address this problem have included providing double foldingflaps and/or tongues in carton blanks to reinforce the corners and, insome cases, gluing special corner reinforcements in cartons to inhibittearing. Such attempts have not been completely successful.

In some situations, a product manufacturer may specify that cartons intowhich products are to packaged be printed on the inside in addition tothe printing of logos and graphics on the outside of the carton. Forexample, a manufacturer may want to print contest rules, productinstructions, special incentive coupons, or the like on the inside ofproduct cartons. In the past, such interior printing has required thatrelatively expensive and time-consuming two-sided printing techniques beused to print both sides of a web from which the carton blanks are cut.Further, since interior surfaces of cartons generally are not coated forprinting, the quality and character of printing available for interiorcarton surfaces has been limited.

A need therefore exists for an improved paperboard carton that providesthe strength and rigidity of cartons made from micro-flute at acompetitive cost. A related need exists for an efficient and costeffective method of making such paperboard cartons that uses traditionalpaperboard carton fabrication machinery and that does not substantiallyincrease material costs associated with the fabrication process. Furtherneeds exist for more efficient methods of providing paperboard cartoninserts such as stiffeners and dividers and for providing higher qualityprinting visible on the interior surfaces of cartons where such printingis desired. It is to the provision of a method of making a paperboardcarton and a resulting carton that addresses these and other needs andthat overcomes the problems of the prior art that the present inventionis primarily directed.

SUMMARY OF THE INVENTION

Briefly described, the present invention, in a preferred embodimentthereof, comprises a method of making reinforced paperboard cartonshaving enhanced strength and rigidity similar to that of micro-flute inselected regions where strength and rigidity are required. The methodcomprises the steps of advancing a web of paperboard along a path. Theweb of paperboard has a predetermined width according to the size ofcartons to be made and preferably is drawn from a large roll ofpaperboard. The web of paperboard may or may not be pre-printed on theside that will become the outside of the finished carton with, forexample, logos and graphics, according to application specificrequirements. The web also may be printed on both sides if desired.

As the web of paperboard is advanced along the path, one or more ribbonsof reinforcing material, each having a width less than the width of thepaperboard web, is progressively applied to the web. Each ribbonpreferably is applied with adhesive to the side of the web that willbecome the inside of the finished cartons and is positioned at apredetermined location across the width of the web. The location of eachribbon is selected to provide multiple layers or laminations of materialin specific regions of finished cartons where enhanced strength and/orrigidity will be required such as, for example, in the side walls of thecarton. Preferably, the ribbons of reinforcing material also are formedof paperboard and most preferably are pre-cut or slit to desired widthsfrom paperboard trim or cull that otherwise may have reduced value. Theribbons are drawn from rolls that are pre-positioned to locate theribbons properly on the web, advanced along and adjacent to the path ofthe web, supplied with adhesive on one side, and progressively broughtinto engagement with and compressed against the advancing paperboard webto adhere the ribbons to the web. In one embodiment, one or more of theribbons may be pre-printed or on both sides with application specificindicia that ultimately will be exposed on the inside of finishedcartons.

After the reinforcing ribbons are laminated to the advancing web, theweb may be cut into sheets of a predetermined size. The sheetssubsequently may be die-cut and scored with fold lines as required toform carton blanks defining the various panels and tabs that ultimatelywill become the walls of finished cartons. The carton blanks may bepalletized and shipped to packagers, where the blanks are converted intocartons and packed with articles such as, for example, beveragecontainers or food items. When converted to cartons, the JD previouslypositioned and applied paperboard reinforcing ribbons form multiplelayers or laminations of paperboard in selected portions of the cartonssuch as, for example, in their sides, where enhanced structuralintegrity is required. By appropriately selecting, sizing, andpositioning the reinforcing ribbons, paperboard cartons having strengthand rigidity comparable or superior to that provided by cartons made ofmicro-flute are obtained. Further, through judicious use of trim andcull in making the reinforcing ribbons, paperboard cartons made by themethod of the present invention can be economically viable alternativesto cartons made of micro-flute.

In addition to providing paperboard cartons comparable in strength tomicro-flute cartons, the present invention offers possibilities that arenot obtainable with micro-flute. For example, the reinforcing ribbons ofthe present invention may be pre-printed on one side with high-qualitygraphics and indicia that is visible on the inside of finished cartons,all without requiring a two-sided printing process. Further, only aportion of one or more ribbons may be adhered to the paperboard web,with another portion being inwardly foldable to define interior cartonstructures such as stiffeners and dividers without the need for theinsertion of a separate liner. Additional advantages are also provided,as will become more apparent below.

Thus, a unique reinforced paperboard carton and method of itsmanufacture is now provided that successfully addresses the problems andshortcomings of the prior art. The carton has structural integritycomparable to cartons previously made of micro-flute but is made oftraditional paperboard material, which is easily converted to cartons inpackaging machines with standard conversion machinery. The carton iseconomically competitive with cartons formed of micro-flute because ofthe unique use of trim and cull in forming the reinforcing ribbons andbecause the method of making the carton blanks can be practiced withexisting paperboard fabrication machinery. The forgoing and otherfeatures, objects, and advantages of the invention will become moreapparent upon review of the detailed description of the preferredembodiments set forth below when taken in conjunction with theaccompanying drawing figures, which are briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustration of a method of making reinforcedpaperboard carton blanks that embodies principles of the presentinvention in a preferred form.

FIG. 2 is a cross-sectional view showing the profile of a carton blankmade by the method illustrated in FIG. 1.

FIG. 3 is a perspective view of a possible configuration of a paperboardcarton blank that embodies principles of the invention.

FIG. 4 is a sectional view illustrating a portion of a reinforcedpaperboard carton blank according to the invention and illustrating apreferred placement of a score line relative to the edge of an adjacentreinforcing ribbon.

FIG. 5 is a sectional view of the portion of the reinforced paperboardcarton blank of FIG. 3 with the blank folded along its fold line as itappears when the blank is converted to a carton.

FIGS. 6 a through 6 h are cross-sectional views of carton blanks made bythe method of the invention illustrating some of the possibleconfigurations in which ribbons of reinforcing material may be appliedto a paperboard base sheet.

FIG. 7 is a perspective view of one configuration of a carton thatembodies principles of the invention illustrating the results ofpre-printing ribbons of reinforcing material with indicia according toone embodiment of the invention.

FIG. 8 is a perspective partially sectioned view illustrating anotherpossible configuration of a carton formed by the method of the inventionand showing various aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, carton blanks may be provided in the form ofpre-glued knocked down sleeves or completely flat sheets depending uponthe type of packaging operation in which they are to be used. The cartonblank shown in FIG. 3 is of the former type and typically is partiallyfolded and glued at the carton manufacturing location and shipped to apackager in the form of a knocked down sleeve. This sleeve, then, iserected by the packaging machinery into an open-ended carton sleeve intowhich product is inserted before the carton sleeve is sealed shut. Thistype of carton typically is used in most beer and soft drink bottlingplants. The carton shown in FIG. 8, on the other hand, typically isformed from a carton blank that is shipped completely flat, foldedaround product in the packaging machine, and glued shut. This lattertype of carton blank is different than the former in that the gluing ofthe carton to form a sleeve is done at the product production and/orpackaging facility rather than at the carton fabricating facility. Thepresent invention will be described for the most part in terms of makinga flat carton blank typified by the carton of FIG. 8. However, it shouldbe understood that the present invention is not limited to thefabrication of flat carton blanks, but also includes the fabrication ofpre-glued knocked down carton sleeve blanks as well as other types ofcarton blanks.

Referring now in more detail to the drawings, wherein like numeralsrefer, where appropriate, to like parts throughout the several views,FIG. 1 illustrates a fabrication line 11 for making reinforcedpaperboard carton blanks according to a preferred embodiment of theinvention. The various stations along the fabrication line 11 areillustrated in simplified functional form for clarity of description. Itwill be understood, however, that the fabrication line and the machinerymaking up the various stations therealong are standard machinery in thepaperboard making industry and are well known by those of skill in theart. Further, a detailed description of the machinery that makes up thefabrication line is not necessary to a complete disclosure andunderstanding of the invention. Accordingly, this machinery is notdescribed in detail here.

The fabrication line 11 in FIG. 1 has an upstream end 12 and adownstream end 13 and the various elements used in the making ofpaperboard blanks according to the invention flow along paths in adirection extending generally from the upstream end toward thedownstream end of the line. A large roll 14 of a paperboard web 17 isrotatably mounted on a pair of mandrels 16 located at the upstream endof the fabrication line 11. In carrying out the method of the invention,the paperboard web 17, which is pre-cut to a required width as describedabove, is drawn from the roll 17 and advanced along a path, generallyindicated by arrows 15, that extends past the various stations of thefabrication line. In one embodiment, the paperboard web 17 may bepreprinted on one side, as indicated at 23, with indicia such asapplication specific graphics, trademarks, and logos; however, suchpre-printing is not desired is some applications and should not beconsidered a requirement or limitation of the invention. Alternatively,the web may printed on both sides, which is desirable for someapplications.

Mandrels 18, three of which are illustrated in FIG. 1, are disposed atspaced locations along the path 15 adjacent the upstream end 12 of thefabrication line 11. Ribbons 21 of reinforcing material, each having awidth less than the width of the paperboard web 17, are rolled ontorelatively narrow rolls 19 and the rolls 19 are rotatably mounted on themandrels 18. The ribbons 21 of reinforcing material are progressivelydrawn from the rolls 19 along with the web 17 and initially are disposedatop and move along the path 15 with the web 17. Each of the mandrels 18may carry multiple rolls 19 of ribbons 21 and each of the rolls 19 maybe positioned at any desired location across the width of the mandrel.Further, each of the ribbons 21 of reinforcing material may be cut toany desired width less than the width of the paperboard web 17.

As the web 17 and ribbons 21 are drawn from their respective rolls andadvance along the path 15, the ribbons are positioned, according to thelocations of their rolls 19 on mandrels 18, at predetermined locationsacross the width of the web 17. In the configuration illustrated in FIG.1, for example, the rolls 19 are positioned such that a double layer ofribbons 21 is located adjacent each of the opposed edge portions of theweb, a single ribbon is located in the central portion of the web, and apair of relatively narrow ribbons are disposed on either side of thecentrally located ribbon. By appropriately positioning the rolls 19 onthe mandrels 18, virtually any placement and configuration of ribbons 21of reinforcing material may be obtained, as described in more detailbelow.

The reinforcing material from which the ribbons 21 are formed may be anyof a variety of appropriate materials such as, for example, thinplastic, fiberglass, woven or non-woven webs, or foam, and these andother materials are considered to be within the scope of the invention.Preferably, however, the ribbons also are made of paperboard and mostpreferably are cut or slit from paperboard trim or cull that otherwisehas little or no commercial value. The invention will be describedhereinafter in terms of ribbons of paperboard reinforcing material forease and clarity of understanding. It should be understood, however,that the term “paperboard” when used in this context is intended toencompass and include any material with the physical and mechanicalattributes necessary to provide the requisite reinforcing properties.

As the paperboard web 17 and ribbons 21 advance along the path 15, theymove through a traditional de-curling station 22, where the paperboardof the web and ribbons is flattened and any curl that may have beeninduced by rolling the paperboard onto rolls 14 and 19 is removed. Fromthe de-curling station 22, the web and ribbons advance further along thepath 15 to a scoring station 24, which includes a pair of rollers 25along which one or more scoring wheels 26 are disposed. The scoringwheels 26 are selectively positioned across the width of the rollers 25to score the web 17 with longitudinally extending fold lines 27, alongwhich carton blanks made by the method of the invention ultimately willbe folded when converted into cartons.

As described in more detail below, some of the fold lines 27 may belocated adjacent or along an edge of a reinforcing ribbon 21. In suchcases, these fold lines preferably are carefully located a predeterminedshort distance from the edge of the ribbon so that the ribbon will notadversely affect or interfere with the folding of the paperboard alongthe fold lines. The scoring wheels 26 shown in FIG. 1 are located toprovide substantially equally spaced fold lines across the width of thepaperboard web 17. It will be understood, however, that any number offold lines at any number of locations across the web, or no fold lines,determined by the desired final shape and size of cartons being made,are possible and within the scope of the invention.

With the fold lines 27 scored in the paperboard web 17, the web 17advances along the path 15 to a pair of guide rollers 31 and thepaperboard reinforcing ribbons 21 diverge from the web 17 and advance toa gluing station 28 for receiving adhesive. In the illustratedembodiment, the gluing station 28 comprises an array of traditionaladhesive applicators 29, each having a pair of nip rollers 32 betweenwhich one or more paperboard reinforcing ribbons pass. The lower niproller 32 of each of the applicators 29 is partially immersed in anappropriate liquid adhesive contained within a flooded nip bath 33. Asthe paperboard reinforcing ribbons 21 pass between the nip rollers, alayer of adhesive is transferred from the lower nip roller of each pairto the bottom side (as seen in FIG. 1) of each ribbon 21. An array ofthree adhesive applicators 29 are illustrated in FIG. 1 for applyingadhesive to the seven paperboard reinforcing ribbons in the illustratedembodiment. Fewer or more than three adhesive applicators 29 may be usedas necessary depending upon the number and configuration of reinforcingribbons required in a particular application.

Means other than nip rollers and nip baths for applying adhesive to theribbons may be used to apply adhesive to the ribbons such alternativemeans include adhesive sprays, which commonly are used in the paperboardindustry. Adhesive spraying mechanisms for use in the paperboardindustry are commercially available and may be obtained, for example,from the Nordson Company. In any case, adhesive may be applied to thereinforcing ribbons 21 in a continuous coat, a discontinuous coat, astitch-glued pattern, a strand, or otherwise. Preferably, the adhesiveis applied in such a way as to minimize the amount of adhesive requiredto provide adequate paperboard to paperboard bonding. In one embodimentof the present invention, adhesive is applied along only one side of oneor more of the ribbons to produce a finished carton having inwardlyfoldable internal structures such as separators and stiffeners, asdescribed in more detail below.

The paperboard web 17 advances from the guide rollers to the compressionstation 34, which includes a pair main compression rollers 36, that alsomay function as pull rollers. Likewise, the adhesive bearing paperboardribbons 21 advance from the gluing station 28 toward the compressionstation 34 and toward the paperboard web 17. At the compression station34, the paperboard ribbons 21 and paperboard web 17 pass between themain compression rollers 36. The compression rollers 36 are set tocompress the reinforcing ribbons 21 and the web 17 together withsufficient pressure to bond the adhesive and thus the ribbons to theweb, or to other underlying ribbons in cases where multiple laminationsof ribbons are to be applied to the web 17. In this way, the ribbons areprogressively applied to the advancing web of paperboard at selectedlocations across the width of the web, as determined by the placement ofrolls 19 on mandrels 18.

From the compression station 34, the paperboard web 17 with scored foldlines 27 and with the paperboard reinforcing ribbons 21 laminatedthereto proceeds toward the downstream end 13 of the fabrication line 11and toward a cutting station 37. In the illustrated embodiment, thecutting station 37 includes a traditional rotary knife assembly 38,which rotates to cut the web 17 across its width into rectangular sheetsof a predetermined size. Each sheet has a width equal to the width ofthe paperboard web 17 and a length determined by the settings andoperation of the rotary knife assembly 38. Means other than a rotaryknife such as, for example, a traversing knife assembly or a platencutter may be substituted for the rotary knife of the illustratedembodiment and these and other means for cutting the web should beconsidered equivalent to the illustrated rotary knife assembly.

Once the web 17 is cut into sheets 39, the sheets may be stacked anddelivered to a die cutter, where the sheets are cut in a standard platendie-cutting operation to form carton blanks having the various tabs andpanels necessary to form paperboard cartons embodying principles andfeatures of the present invention.

As an alternative to cutting the web 17 into sheets 39 and subsequentlydie-cutting the sheets 39 to form paperboard blanks, the rotary knifeassembly 33 in FIG. 1 may be replaced with a platen die cutter or rotaryinline die cutter, in which case the web 17 is cut immediately intocarton blanks at the downstream end of the fabrication line 11 and thestep of first cutting the web into sheets is eliminated. In either case,once the carton blanks are cut, they may be palletized and shipped toproduct packagers, where the blanks are converted into cartons andpacked with articles in the usual way.

When the blanks are converted, the ribbons of reinforcing paperboardlaminated to the carton blanks form multiple layers of paperboard inselected portions of the cartons and thus reinforce the cartons in theseportions. The locations of the ribbons are carefully determined inadvance such that, when the carton blank is converted to a carton, theribbons and thus reinforcement is provided in selected portions of thecartons such as, for example, in their side walls, where added strengthand/or rigidity are required. Reinforced paperboard cartons made by themethod of this invention have been found to exhibit strength andrigidity in the reinforced portions that is comparable or superior tothat of cartons made from micro-flute.

With the forgoing specific example in mind, it will be appreciated that,in one embodiment, the present invention is a unique method of makingreinforced paperboard cartons. The method includes the steps ofadvancing a web of paperboard along a path, the web of paperboard havinga width. At least one ribbon of reinforcing material having a width lessthan the width of the paperboard web is progressively applied,preferably with adhesive, to the advancing web at a predeterminedposition across its width. The web with its applied reinforcing ribbonis cut to form carton blanks and the carton blanks are formed intocartons for receiving articles, the ribbon of reinforcing materialproviding reinforcement in selected portions of the cartons where addedstrength is required.

FIG. 2 is a cross-sectional view of the web 17 of FIG. 1 as it appearsafter the reinforcing ribbons 21 have been bonded to the web, such asjust beyond the compression station 34. While this particularconfiguration may or may not correspond to that of an actual carton, itis presented along with FIG. 1 to illustrate clearly some of the varietyof possible sizes and placements of reinforcing ribbons 21 and scoredfold lines 27 that may be obtained through the method of the invention.In FIG. 2, the reinforcing ribbons 21 are applied at predeterminedlocations across the width of the web 17 such that a double layer ofribbons is disposed adjacent each edge portion of the web and a singleribbon is located intermediate the edges of the web. A relatively thinribbon is located on either side of the centrally located ribbon and theweb is scored to form longitudinally extending fold lines 27 spaced ashort distance from the edges of some of the reinforcing ribbons.

FIG. 3 illustrates one possible configuration of an actual carton blankthat may be formed by the method of the invention. The carton blank 51has a base sheet 55 of paperboard material, which is a part of thecontinuous web of paperboard used to make the blank 51 according to theinvention. The base sheet 55 has longitudinally extending fold lines 53,which were scored at a scoring station 24 of a fabrication line 11 (FIG.1), and transversely extending fold lines 52, which were scored duringthe die-cutting process. The fold lines 52 and 53 define a top panel 54,a bottom panel 56, a first side panel 57, and side panel tabs 58 and 59,which overlie one another when the carton blank is converted to form asecond side panel of the carton. End tabs 61 are formed outboard of thelongitudinally extending fold lines 53 and the end tabs are configuredto be folded inwardly along the fold lines 53 when the blank isconverted to form the ends of the carton.

Paperboard reinforcing ribbons 62 are laminated to the base sheet 55according to the method of the invention. The reinforcing ribbons 52 arepositioned along and increase the effective thickness of the end tabs 61to reinforce the end tabs and provide enhanced structural integrity inthe end portions of a carton converted from the blank. During conversionof the blank 51 into a carton, the various panels and tabs of the blankare folded generally inwardly along the scored fold lines 52 and 53 asindicated by arrows 60, and selected ones of the tabs are securedtogether with adhesive or otherwise to form a rectangular carton to bepackaged with articles. The carton, when formed, has ends defined by theend tabs 61 that are reinforced by the paperboard reinforcing ribbons 62laminated thereto to provided enhanced strength, rigidity, and tear orblow-out resistance in the ends of the carton. Thus, when the blank 51is converted, it forms a reinforced paperboard carton having a pluralityof panels defining sides and ends of the carton an a layer ofreinforcing paperboard material applied to selected ones of the panelsto reinforce the carton in selected regions defined by the reinforcedpanels.

FIGS. 4 and 5 illustrate a preferred placement of the reinforcingpaperboard ribbons 62 with respect to adjacent fold lines 53 in FIG. 3to insure that the added thickness of the ribbons does not interferewith the folding of the carton blank along the fold lines duringconversion. Specifically, the paperboard base sheet 55 has alongitudinally extending fold line 53 that defines an end tab 61 of thecarton blank. Reinforcing paperboard ribbon 62 is laminated to the basesheet 55 in the region of the end tab 61 according to the presentinvention to provide reinforcement as described above. The inboard edge65 of the ribbon 62 is spaced a predetermined short distance from thefold line 53. Thus, when the sheet 55 is folded along fold line 53during conversion to a carton, as illustrated in FIG. 5, the spacebetween the edge 65 of the ribbon and the fold line insures that theedge of the ribbon does not impact any of the panels of the blank orotherwise interfere with the folding process.

It has been found that a distance between a fold line and an edge of areinforcing ribbon of about 0.030 inches, which is an industry standardpaperboard thickness, allows unimpeded folding of a carton blank alongthe fold line while having little or no effect on the structuralreinforcement provided by the reinforcing ribbon. It also has been foundthat a distance of about 0.030 inches is easily achieved and maintainedwhen performing the method of this invention with standard paperboardmaking machinery as illustrated in FIG. 1. Of course, distances otherthat the preferred distance may be chosen according to applicationspecific requirements and any appropriate distance is intended to bewithin the scope of the invention. Further, in some applications,reinforcing ribbons may be applied at locations on the paperboard webother than adjacent to fold lines. In these cases, the distance betweenedges of the ribbon a and fold lines generally is not critical.

FIGS. 6 a through 6 h are provided to illustrate some of the manypossible configurations in which reinforcing ribbons may be applied to apaperboard web using the method of the present invention. Each of thesefigures is a cross-sectional view of a web with reinforcing ribbonsapplied thereto and longitudinally extending fold lines are scored insome of the figures. It should be understood that these figures do notnecessarily represent configurations corresponding to actual cartonblanks, but instead are generally simplified drawings selected forclarity in describing some of the many possible configurations ofreinforcing ribbons. Also in this regard, the thickness of thepaperboard web and reinforcing ribbons generally is exaggerated in FIGS.6 a through 6 h for clarity of illustration.

In FIG. 6 a, a the paperboard web forms a base sheet 66 havingreinforcing paperboard ribbons 67 laminated thereto and extending alongthe opposed edge portions of the base sheet. Fold lines 68 are scored inthe base sheet extending along and adjacent to the inboard edges of thereinforcing ribbons 67 to facilitate folding of the base sheet in theformation of a carton. A configuration of reinforcing ribbons similar tothat of FIG. 6 a may be selected, for example, when forming cartonblanks such as the blank 51 illustrated in FIG. 3.

FIG. 6 b illustrates a possible configuration similar to that of FIG. 6a but having a double thickness paperboard base sheet 69 formed from afirst paperboard sheet 71 and a second paperboard sheet 72 laminatedtogether. Reinforcing ribbons 73 are applied along the opposed edgeportions of the base sheet 69 and fold lines 74 are scored in the basesheet to facilitate folding. Referring to FIG. 1, a configurationsimilar to that of FIG. 6 b may be made by the method of the inventionby, for example, mounting a second roll of full width paperboard on themandrel 18 immediately upstream of the mandrel 16. Alternatively, a rollof double thickness laminated web may be made in advance in a separateprocess and mounted on mandrel 16.

FIG. 6 c illustrates the possibility of applying multiple laminations ofreinforcing ribbons, one atop the other, to provide even morereinforcement in areas where further enhanced structural integrity maybe required. In this figure, three stacked reinforcing ribbons 78 areapplied along the opposed edge portions of a base sheet 76, to formmultiply laminated reinforcing strips 77. Such a configuration may beformed by the method illustrated in FIG. 1 by aligning rolls 19 ofreinforcing ribbons with each other on successive mandrels 18 so thatthe reinforcing ribbons overlie one another as they are drawn from theirrespective rolls. Alternatively, rolls of multi-ply pre-laminatedreinforcing ribbons may be made in advance and mounted on mandrels 18 ifdesired to obtain similar results.

FIG. 6 d illustrates the ability to apply multiple reinforcing ribbonsat selected locations across the width of a paperboard web using themethod of the invention. Here, three reinforcing ribbons 81 are appliedto a paperboard base sheet 82, two along the opposed edge portions ofthe base sheet and one intermediate the edge portions. While thereinforcing ribbons 81 in FIG. 6 d are illustrated with substantiallythe same width, it will be understood that each ribbon may have adifferent width and may be positioned at any desired location across thewidth of the base sheet according to a desired configuration andreinforcement requirements of a finished paperboard carton. Selectiveplacement of the reinforcing ribbons is achieved in the methodillustrated in FIG. 1 by selectively positioning the rolls 19 ofreinforcing ribbon across the width of mandrels 18.

FIG. 6 e illustrates the possibility of applying selectively positionedmulti-layer reinforcing ribbons to a paperboard base sheet. Multiplelayers of reinforcing ribbons 84 are applied atop each other on a basesheet 82 to form reinforcing strips 83, one extending along each of theopposed edge portions of the base sheet and one positioned intermediatethe edge portions. Of course, any number of strips 83 may be applied,each of the ribbons 84 and resulting strips 83 may be any desired width,and the strips may be applied at any desired location across the widthof the base sheet 82.

FIG. 6 f shows the possibility of applying multiple reinforcing stripsformed of multi-layer reinforcing ribbons at selected positionsintermediate the edge portions of a base sheet. Multiple reinforcingstrips 87 each formed of multiple layers of reinforcing ribbons 88 areapplied to the base sheet at selected locations on the base sheet 86 notextending along the edge portions thereof.

FIG. 6 g illustrates a configuration possible with the method of theinvention wherein one or more reinforcing strips 91 applied to a basesheet 89 is formed of multiple layers of reinforcing ribbons 92 and 93the reinforcing ribbon 93 having a width less than the width ofreinforcing ribbon 92. Any number of layers of ribbons may be applied inthis manner to form multi-layer reinforcing strips with each ribbon ofthe strips having a width different from the widths of the other ribbonsof the strips, according to application specific requirements. Arelatively narrower reinforcing ribbon 94 is applied in FIG. 6 g to thebase sheet 89 at a selected location intermediate its edges. Thus,multiple reinforcing ribbons each having different widths may be appliedat any desired location across the width of the base sheet through themethod of the present invention.

FIG. 6 h illustrates a unique application of the method of thisinvention to form internal structures of a carton such as, for example,L-brackets, stiffeners, and separators. A ribbon 97 is applied to a basesheet 96 according to the method of the invention. In this case,however, the method includes applying adhesive along only one side ofthe ribbon before bonding the ribbon to the paperboard web. The ribbon97 has a fold line 101 scored therein and the fold line separates theribbon into a first section 98 and a second section 99. Adhesive isapplied to the first section 98, which is bonded to the base sheet 96,and the second section 99 is free to be folded along fold line 101 asindicated by arrow 102 to project in a direction away from the basesheet 96.

The fold line 101 in the ribbon 97 may be scored at the scoring station24 (FIG. 1) or, alternatively, the ribbon may be pre-scored prior towinding it onto a roll 19. In any case, the second portion 99 of theribbon functions in the final carton as an internally extendingstructure. Methods of providing adhesive to only a portion of the ribbon97 as illustrated in FIG. 6 h are known in the paperboard industry andmay include, for example, masking techniques and/or spraying theadhesive onto the selected portion ribbon as it advances along thefabrication line 11 (FIG. 1).

FIG. 7 illustrates one of the many possible configurations of cartonsthat may be made by the method of the present invention. The carton 106,which may, for example, be a shipping and display container for fooditems such as candy bars, is converted from a carton blank madeaccording to the invention and has front and back walls 107, end walls108, and a floor 110. The front and back walls 107 of the carton arestructurally reinforced with paperboard reinforcing ribbons 109 appliedto the insides of the panels that form the walls 107. Thus, the frontand back walls 107 of the carton 106 exhibit enhanced strength andrigidity as a result of the reinforcing ribbons. These properties may bedesirable, for example, to enhance the stackability of the cartons whenpackaged with product, to resist blow-out during shipment, or to provideresistance to tearing in the corners or other high stress locations ofthe carton.

Further according to the invention, the reinforcing ribbon 109 on theback wall 107 of the carton 106 is seen to have been pre-printed withindicia that is visible on the inside of the carton. Thus, the method ofthis invention may eliminate the requirement of double sided printing ona carton base sheet when it is desired to display indicia on the insideof a carton. In FIG. 7, the indicia 101 is illustrated as a savingscoupon; however, any form of indicia such as, for example, instructions,contests rules, special graphics, or otherwise may be provided. Further,because the reinforcing ribbon is pre-printed, it may be provided with acoated or primed printing surface, which allows high-quality graphics tobe printed, on the reinforcing ribbon. This is an economical improvementover previous internal printing, which, as mentioned above, has beensomewhat limited in available printing quality.

In addition or as an alternative to the printing of indicia, reinforcingribbons may be pre-coated if desired with a moisture resistant or othertype of coating. In such cases, the method of this invention may be usedto make efficiently produced lined cartons for use as alternatives tocartons such a detergent boxes, which traditionally have been suppliedwith separate individually inserted liners.

FIG. 8 illustrates another configuration of a reinforced paperboardcarton made according to the method of the invention. The end of thecarton is shown in cross-section to illustrate better the internalstructural components of the carton. The carton 116, which isillustrated as a carton for packaging fruit drink, is generallyrectangular in shape and is folded along fold lines 125 to define sidewalls 117, a bottom wall 118 and a top wall 119. The top wall 119 isformed by overlapping flaps 120 and 121, which may be secured togetherby any appropriate means such as with adhesive, and may be provided witha cut-out 122 if desired to form a carrying handle. The side walls 117have outside surfaces formed by respective panels 124. Reinforcingribbons 123, which preferably also are made of paperboard, are appliedto the side wall panels 124 on the inside of the carton according theinvention and form the inside surfaces of the side walls 117. Aspreviously discussed, the reinforcing ribbons 123 enhance the structuralintegrity of the side walls 117 to provide increased strength andrigidity in the sides of the carton for stackability and resistance tocarton blow-out. At least one of the reinforcing ribbons 123 is seen tobe printed with indicia 127 that is exposed on the inside of the cartonand that may become apparent to a consumer as product is removed fromthe carton.

Paperboard dividers and stiffeners 126 are applied as described aboverelative to FIG. 6 h to the bottom wall 118 and the top wall 119 on theinside of the carton 116. Each of the dividers and stiffeners is formedfrom a ribbon of paperboard applied according to the method of theinvention and has a first portion 129 bonded to the respective wall anda second portion or flap 128 that is folded to extend internally intothe carton. The flaps 128 may function to provide structural stiffnessto the top and bottom walls and/or to provide spacers or protectiveseparators for articles to be packaged in the carton. Indeed, a widevariety of internal carton structures previously provided by separateand expensive inserts may be made economically, efficiently, andvirtually automatically using the method of the present invention.

The invention has been described herein in terms of preferredembodiments and methodologies, which represent the best mode known tothe inventors of carrying out the invention. It will be understood bythose of skill in the art, however, that many additions, deletions,modifications, and substitutions of equivalent elements not specificallyincluded in the preferred embodiments may be made without departing fromthe spirit and scope of the invention as set forth in the claims.

1. A method of making a paperboard carton blank to be folded to form acarton having a top wall, a bottom wall, and two side walls, the cartonhaving an inside and an outside, the method comprising the steps of: (a)advancing a web of noncorrugated paperboard along a path, the web ofnoncorrugated paperboard having a first surface which will be on theinside of the carton when the blank is folded to form the carton, awidth, and longitudinally extending panel portions that will each becomea plurality of panels, the longitudinally extending panel portions beingseparated by longitudinal fold lines; (b) laminating at least a firstribbon and a second ribbon of reinforcing material to the first surfaceof the advancing web of noncorrugated paperboard, the first ribbon andthe second ribbon having a width less than the width of the web ofnoncorrugated paperboard, the first ribbon being positioned on, andadhered to, substantially all of, but not beyond, a first longitudinallyextending panel portion of the web of noncorrugated paperboard, and thesecond ribbon being positioned on, and adhered to, substantially all of,but not beyond, a second longitudinally extending panel portion of theweb, the first ribbon and the second ribbon not extending across thelongitudinal fold lines; and (c) cutting the web of noncorrugatedpaperboard and the laminated first ribbon and second ribbon across theirlength into a carton blank having panels corresponding to the top wall,the bottom wall, and the two side walls of the carton, whereby the firstribbon and the second ribbon are positioned on the inside of the cartonwhen the carton blank is folded to form the carton, and reinforce thecarton blank.
 2. The method of claim 1 wherein at least one of the firstribbon or the second ribbon of reinforcing material comprisespaperboard.
 3. The method of claim 2 and wherein at least one of thefirst ribbon or the second ribbon of paperboard comprises paperboardtrim.
 4. The method of claim 2 wherein at least one of the first ribbonor the second ribbon of paperboard comprises paperboard cull.
 5. Themethod of claim 1 and wherein step (b) comprises advancing the firstribbon and the second ribbon of reinforcing material along paths,applying adhesive to the first ribbon and the second ribbon ofreinforcing material, and bringing the first ribbon and the secondribbon into contact with the web to adhere the first ribbon and thesecond ribbon to the web.
 6. The method of claim 1 wherein at least afirst edge panel portion extends along opposed edges of thenoncorrugated paperboard web and wherein the first ribbon of reinforcingmaterial is positioned within the first edge panel portion.
 7. Themethod of claim 1 wherein the web of noncorrugated paperboard hasopposed edges wherein the first panel portion extends along the webintermediate the opposed edges, the first ribbon of reinforcing materialbeing applied within the first panel portion.
 8. The method of claim 1wherein an additional ribbon of reinforcing material is applied atop thefirst ribbon or the second ribbon of reinforcing material to formmultiple layers of reinforcing material.
 9. A method of making apaperboard carton having a top wall, a bottom wall, and two side walls,the carton having selectively reinforced panels, said method comprisingthe steps of (a) advancing a web of noncorrugated paperboard along apath, the web of noncorrugated paperboard having a width andlongitudinally extending panel portions that will each become aplurality of panels, the longitudinally extending panel portions beingseparated by longitudinal fold lines; (b) progressively applying andadhering at least a first ribbon and a second ribbon of reinforcingmaterial to the advancing web of noncorrugated paperboard, the firstribbon and the second ribbon having a width less than the width of theweb of noncorrugated paperboard, the first ribbon being positioned tooverlie and adhere to substantially all of, but not beyond, a firstselected longitudinally extending panel portion of the web, and thesecond ribbon being positioned to overlie and adhere to substantiallyall of, but not beyond, a second selected longitudinally extending panelportion of the web, the first ribbon and the second ribbon not extendingacross the longitudinal fold lines; (c) cutting the web of noncorrugatedpaperboard to form a carton blank having panels corresponding to the topwall, the bottom wall, and the two side walls of the carton; and (d)forming the blank into the carton for receiving articles, the cartonhaving an inside and an outside, the first ribbon and the second ribbonof reinforcing material reinforcing the carton and being positioned onthe inside of the carton.
 10. The method of claim 9 wherein at least oneof the first ribbon or the second ribbon of reinforcing materialcomprises noncorrugated paperboard.
 11. The method of claim 9 whereinstep (b) further comprises advancing the first ribbon and the secondribbon of reinforcing material along a path, applying adhesive to theadvancing first ribbon and the advancing second ribbon, andprogressively bringing the first ribbon and the second ribbon intoengagement with the advancing web of noncorrugated paperboard to adherethe first ribbon and the second ribbon to the web.
 12. The method ofclaim 9 wherein the longitudinally extending panel portions include afirst edge panel portion and a second edge panel portion, the first edgepanel portion and the second edge panel portion extending along opposededges of the web of paperboard and wherein at least the first ribbon ispositioned to overlie substantially all of, but not beyond, the firstedge panel portion.
 13. The method of claim 9 wherein step (b) furthercomprises applying and adhering atop the first ribbon or the secondribbon of reinforcing material an additional ribbon of reinforcingmaterial to form a double thickness of reinforcing material.
 14. Themethod of claim 9 wherein the longitudinal fold lines include a firstlongitudinal fold line and a second longitudinal fold line, wherein anintermediate longitudinally extending panel portion extends between thefirst longitudinal fold line and the second longitudinal fold line, andwherein the first ribbon is positioned to overlie substantially all of,but not beyond, the intermediate panel portion.
 15. The method of claim9 further comprising the step of printing indicia on at least one of thefirst ribbon or the second ribbon of reinforcing material, the indiciabeing visible from the inside of the carton formed in step (d).
 16. Themethod of claim 15 wherein the indicia is printed on at least one of thefirst ribbon or the second ribbon of reinforcing material before beingapplied and adhered to the web of noncorrugated paperboard in step (b).17. The method of claim 9 further comprising the step of scoring foldlines to separate the longitudinally extending panel portions of the webof noncorrugated paperboard.
 18. The method of claim 17 wherein thefirst ribbon or the second ribbon of reinforcing material has an edgeand wherein the step of scoring fold lines includes forming at least onefold line adjacent the edge of the first ribbon or the second ribbon.19. The method of claim 9 where at least one of the first ribbon or thesecond ribbon of reinforcing material comprises paperboard trim.
 20. Themethod of claim 9 wherein at least one of the first ribbon or the secondribbon of reinforcing material comprises paperboard cull.
 21. The methodof claim 9, wherein the longitudinal fold lines are on the same side ofthe web as the first ribbon and the second ribbon.
 22. The method ofclaim 9, wherein step (b) includes progressively applying and adheringat least a third ribbon to the advancing web, the third ribbon beingpositioned not to overlie any of the longitudinal fold lines, the thirdribbon having a first portion adhered to the web and a second portionnot adhered to the web, whereby the second portion of the third ribbonis capable of being folded in a direction away from the web.
 23. Themethod of claim 22, wherein the first portion and the second portion ofthe third ribbon are divided by a fold line.
 24. The method of claim 22,wherein the first portion and the second portion of the third ribbon aredivided by a longitudinally extending fold line, and the second portionof the third ribbon extends between the fold line and one edge of thethird ribbon.
 25. The method of claim 22, wherein at least a thirdribbon is positioned on the inside of the carton.